People change, some for the worse. And some wake up and realize they’ve been putting themselves through unnecessary hell.
Others, like one person who responded here, wait until they think the kids are old enough to handle it.
And some just don’t want to ‘do’ marriage anymore......is suspect thse two were the type that had rows with both swinging language etc. but enjoyed making up later. 20 years says a lot. The only change was she went to Washington - sin city.